Antenna insulator



April 26, 1966 A. c. VELDHUIS ANTENNA INSULATOR 3 Sheets-Sheet 1 Filed Nov. 18, 1964 R m E V N April 26, 1966 A. c. VELDHUIS 3,248,475

ANTENNA INSULATOR Filed Nov. 18, 1964 3Sheets-Sheet 2 1 N VEN TOR.

" 4 [Maria Vi'lafilzis;

April 1966 A. c. VELDHUIS 3,248,475

ANTENNA INSULATOR Filed Nov. 18, 1964 3 Sheets-Sheet 5 I N VEN TOR.

United States Patent 3,248,475 ANTENNA INSULATOR Albert C. Veldhuis, West Chester, Pa., assignor to Trylon incorporated, Elverson, Pa., a corporation of Pennsylvania Filed Nov. 18, 1964, Ser. No. 412,053 4 Claims. (Cl. 17472) This invention relates to antenna arrays and particularly to a unitary insulator adapted for use in making electrical connections between each conductor of an antenna feed line and opposing dipole elements while at the same time providing the necessary insulation between the feed lines and also between the dipole elements.

The insulator of the present invention may be used to particularly advantage in an antenna array in which a plurality of dipole elements are required to be fed by a transmission line with transposed feed-line connections at the successive dipoles. One example of such an antenna array is a horizontally-polarized logarithmicallyperiodic antenna.

A preferred form of the insulator of the present invention is illustrated in the drawings wherein:

FIG. 1 is a perspective illustration of a portion of a horizontally-polarized log-periodic antenna showing five of the insulators used to make transposed connections from the transmission line to five successive pairs of dipole elements;

FIG. 2 is an enlarged perspective of one of the insulators of FIG. 1; r

FIG. 3 is a partially exploded view of the insulator of FIG. 2;

FIG. 4 is a detailed view in section along/the line IVIV of FIG. 2 looking in the direction of the arrows; and

FIG. 5 is a perspective view illustrating a different The individual dipole elements of each dipole are spaced apart axially on a common axis, with the insulator 20 of the present invention occupying the space therebetween.

In the antenna array illustrated, all of the dipole elements are horizontally disposed, being substantially, parallel to the ground. The dipole elements are connected at their inner ends to one or theother'of the conductors 41, 42 of a feed transmission line. A two-conductor transmission line is shown and the insulator of the invention will be herein described with the reference to the two-conductor transmission line shown. However, so far as the insulator of the invention is concerned, the feed transmission line could justas well be a four-conductor line.

The dipole elements are supported at their outer ends by catenary wires 31 and 32, which may preferably be unitary Fiberglas catenaries suspended between guyed steel towers, not shown. Suitable insulators 33, support wires 34, and T-connectors are used to support the dipole elements from the catenaries 31, 32.

The feed transmission-line conductors 41, 42 are shown as stranded conductors, and are of copper or other metal of good conductivity. They run lengthwise along the center axis of the antenna array. The individual conductors 41, 42 of the'feed line lie one above the other in the same or substantially the same vertical plane. The transversely disposed dipole elements lie in a horizontal plane located midway, or about midway, between the two feed-line conductors.

"ice

In the particular antenna being illustrated, the electrical connections between the feed-line conductors 41, 42 and the dipole elements are required to be transposed at successive dipoles. That is, each feed-line conductor is connected to a dipole element first on one and then on the opposite side of the center plane. For example, in FIG. 1, the upper feed-line conductor 41 is connected successively to dipole elements 21b, 22a, 23b, 24a, and

2511, while the lower feed-line conductor 42 is connectedsuccessively to dipole elements 21a, 22b, 23a, 24b, 25a.

In accordance with the present invention, the connections between the two feed transmission-line conductors 41, 42 and each pair of dipole elements are made using a unitary insulator 20 having aform such as is illustrated generally in FIG. 1 and in detail in FIGS. 2, 3 and 4. Each insulator 20 includes a rigid insulator rod 45, preferably cylindrical and preferably of mechanicallyand electrically suitable material, such as porcelain, steatite, of Fiberglas. Opposite ends of insulator rod 45 are provided with Y-fittings 43, 44, of cast aluminum, bronze, stainless steel, or other suitable non-corrosive material. Each Y-fitting is identical to the other and it will only be necessary to describe one of them. Y-fitting 44 will be described.

Y-fitting 44 has a body portion 44a, a base portion 44b, preferably slotted, and a tubular arm 44c which extends angularly from the fitting from a junction point just above the base portion 44b. The body portion44a has an annular flange 44d and an axial recess 44e having a crosssection similar to that of rod 45, preferably circular for receiving the end of the insulator rod 45 which is preferably cylindrical. The end of the rod 45 is cemented or otherwise secured in the recess 44e as by an epoxy 46. Poured lead, or cement, etc. may be used, if desired.

The bore of tubular arm 44c of the Y-fitting 44 communicates with a slot 44 in the base 44b, thereby providing a through passage through'the arm and base, The slot 44 is on one side of the base 44b so that a straight rod or wire may be pushed without bending through the slotted base 44b and tubular arm 440.

A tubular extension 48, preferably of stainless steel or other suitable non-corrosive material, is fitted into the bore of the tubular arm 44c and extends outwardly therefrom to the vertical center plane which passes through thecenter of the insulator rod 45, this plane being indicated in FIG. 4 by the dotted line 50. A similar tubular extension 47 is fitted into the tubular arm 430 of the other Y-fitting 43. The Y-fittings 43 and 44, at opposite ends of the insulator rod 45, are so oriented relative to the rod 45 that one of the tubular extensions (extension 47) extends angularly downward While the other (extension 48) extends angularly upward. The Y-fittings are so cast that the angle between the tubular extension and the rod 45 may preferably be 30, but may be another suitable angle, preferably between 30 and 45. The outer ends of extensions 47, 48 are preferably flared.

The manner of using the new insulator 20, just described, for connecting electrically two dipole elements to two (or more) feed-line conductors will now be described. My new insulator is particularly sui=ted for use in conjunction with a form of mechanical splice produced and sold by Preformed Line Products Company, of Cleveland, Ohio, and this form of splice is illustrated in FIGS. 1-4 of the drawing. However, other known forms of connectors may be used, and I have illustrated in FIG. 5 a known form of right angle crimp connector.

Returning now to FIGS. 1-4, the mechanical splice I connector there shown, known commercially as the PLP splice, is shown in US. Patent 3,032,964, issued May 8, 1962 to Thomas F. Peterson, assigned to Preformed Line Products Company. The PLP form of mechanical splice comprises group of parallel helically-preformed open-pitch copper-conductor strands adapted to be applied to the cable being spliced from the side and adapted to wrap around and to ti htly grip the cable. In the present application, the cable being spliced at one end of the PLP splice is one of the dipole elements and at the other end is one of the feed-line conductors.

Assuming that the PLP type of mechanical-splice connector is to be used with the insulatorof the present invention in an antenna array such as illustrated in FIG. 1, the manner of making the connection between the first set of dipole elements 21a, 21b and the feed-line Wires 41, 42 may be as follows: Assume that the outer end of the stranded cable which is to function as dipole element 21b is already connected to and supported by the catenary 32. The inner end of Zlb is then pushed through the slot 44f at the base 440 of the Y-fitting 44 and out the tubular arm 4 th until a substantial portion is exposed. The tubular extension 48 is slipped over the exposed protruding end of the dipole element 21b and the extension 48 is fitted into the bore of arm 44]), leaving a considerable portion of 21!) still exposed and protruding from the flared end of extension 48.. The half portion 61a (FIG. 3) of one of the helical preformed open-pitch PLP splices 61, is wrapped coaxially around the exposed protruding end portion of the dipole element 21b, and then the half portion 62a of a second helical preformed open-pitch splice 62 is wrapped coaxially and coextensively around the same exposed portion of element 21b, the second splice 6.2a occupying the open pitches of the first splice portion 61a. In this manner, a tubular wrapping is formed about the protruding end portion of the dipole element 21b, as seen in FIG. 3. elastically tightly grips the element 21b, preventing withdrawal of the element 21b from the wrappings 61a, 62a. In this manner, the splice to the dipole element is formed.

The outer half portions oll) and 62b of the preformed splice elements 61 and 62 extend in opposing directions along the stranded feed-line conductor 41, as seen in FIG. 3, and these portions of splice elements 61, 62 are then wrapped around the stranded feed-line conductor it to form the mechanical splice best seen in FIG. 2. The dipole element 21b is then pulled, downward and to the right as viewed in the drawings, until the tubular wrapping formed by 61a, 62a is entirely within the rigid extention 4-3 and the flared end of the extension 43 is flush against the feedline conductor 41, as shown in FIG. 2. The stranded dipole element 211; is bent at the slot 44 so that the major portion of dipole element 21b is located on the extended axis of insulator rod 45, as in FIG. 2.

The other dipole element 21a is attached by a similar series of steps to the lower feed-line conductor 42.

In a manner such as described above, the insulators 2d are installed and connections to the feed transmission line are made. It will be seen that a single unitary insulator 2t) (the unitary structure may be assumed to include the extensions 4-7, 48) enables effective electrical connections to two (or more) feed-line conductors from both dipole elements. It will further be seen that by merely rotating the insulator 2t) 180 about the axis of the insulator rod 45 the insulator is positioned to make reverse connections from the feed-line conductors to the dipole elements. Thus, the single unitary insulator 20 is adapted for use in an antenna array having a transposed transmission or feed line.

It will be understood that for an antenna connection to be satisfactory, consideration must be given to such factors as electrical loss, flashover, wind-loading, strength, etc. Prior art insulators of which I have knowledge are not nearly as satisfactory as the insulator described herein. For example, prior art insulators are more prone to misalignment, and this tends to create stresses in the insulation which must as a consequence be made extra strong to withstand the stresses. In contrast thereto, the new insulator adapts itself to misalignment. Other advantages include ease of application, clean con- This wrapping used in conjunction with known forms of connectors other than the PLP mechanical-splice connector shown in FIGS. 1-4. ()ne such other known form is illustratev in FIG. 5, wherein dipole element 21b is shown connected electrically to feed-line conductor 41 by means of a known form of right angle crimp connector 7%). Connector comprises a pair of C-crimp elements 7% and 7011 connected by a connection 7ilc. The C-elernents are slipped over the stranded dipole element 21b and over the stranded feed conductor 41 and then closed. The dipole element Zllb is then pulled, to the right as viewed in FIG. 5, pulling the C-clamp element 79a into the tubular extension 43 and forming the connection shown in FIG. 5.

While the preferred embodiment of this invention has been described in some detail, it will be obvious to one skilled in the art that various modifications may be made without departing from the invention as hereinafter claimed.

Having described my invention, I claim:

1. An antenna insulator for connecting antenna elements to transmission-line conductors, said insulator comprising a rod of insulating material having a Y-fitting secured at each opposite end thereof, each of said Y-fittings having a body portion, a base portion, and an angularly-disposed tubular arm disposed at an angle of about 3045 relative to the axis of the insulator rod, each said tubular arm having a rigid tubular extension fitted thereinto, said body portion having a recess receiving said insulating rod, said base portion having a slot in commie nication with the bore of said tubular arm providing a passage for an electrical connection between an antenna element and a transmission-line conductor, the angularly' disposed tubular arms of the Y-fittings at opposite ends of said insulating rod projecting in opposing directions.

2. An antenna insulator as claimed in claim 1 further characterized in that the two extensions extend in opposing directions along substantially parallel lines.

3. In combination; a pair of antenna elements; a pair of transmission-line conductors; and an insulator connecting said antenna elements to said transmission-l ne conductor, said insulator comprising a rod of insulating material having a Y-fitting secured at each opposite end thereof, each of said Y-fittings having a body portion, a base portion, and angularly-disposed tubular arm disposed at an angle of about 30-45 relative to the axis of the insulator rod, each said tubular arm having a rigid tubular extension fitted thereinto and extending in opposing directions along substantially parallel lines, said body portion having a recess receiving said insulating-rod, said base portion having a slot in communication with the bore of said tubular arm providing a passage for an electrical connection between an antenna element at the base end of said Y-fitting and a transmission-line conductor at the outer end of said tubular extension, said antenna element extending through said passage into said tubular extension and connected to said transmission-line conductor by a mechanical splice comprising a pair of stranded helically-preformed open-pitch elements of electrical conducting material.

4. In combination; a pair of antenna elements, a pair of transmission-line conductors; and an insulator connecting said. antenna elements to said transmission-line conductors, said insulator comprising a rod of insulating material having a Y-fitting secured at each opposite end thereof, each "of said Y-fittings having a body portion, a base portion, and angularly-disposed tubular arm disposed at an angle of about 3045 relative to the axis of the insulator, each said tubular arm having a rigid tubular extension fitted thereinto and extending in opposing directions along substantially parallel lines, said body portion having a recess References Cited by the Examiner receiving said insulating rod, said base portion having a UNITED STATES PATENTS slot in communication with the bore of sad tubular arm providing a passage for an electrical connection between 452,017 5/1891 Lleb 174169 X an antenna element at the base end of said Y-fitting and 5 1,644,266 10/1927 Ome 174 160 X 2,066,790 1/1937 Matthes 174160 X a transmission llne conductor at the outer end of sand tubular extension, said antenna element passing through 2,825,752 3/1938 Knutz et a1 X said passage into said tubular extension and being con- I nected to said transmission-line conductor by a right-angle ROBERT SCHAEFER Acting Examiner crimp connector. 10 LARAMIE E, ASKIN, Examiner, 

1. AN ANTENNA INSULATOR FOR CONNECTING ANTENNA ELEMENTS TO TRANSMISSION-LINE CONDUCTORS, SAID INSULATOR COMPRISING A ROD OF INSULATING MATERIAL HAVING A Y-FITTING SECURED AT EACH OPPOSITE END THEREOF, EACH OF SAID Y-FITTINGS HAVING A BODY PORTION, A BASE PORTION, AND AN ANGULARLY-DISPOSED TUBULAR ARM DISPOSED AT AN ANGLE OF ABOUT 30*-45* RELATIVE TO THE AXIS OF THE INSULATOR ROD, EACH SAID TUBULAR ARM HAVING A RIGID TUBULAR EXTENSION FITTED THEREINTO, SAID BODY PORTION HAVING A RECESS RECEIVING SAID INSULATING ROD, SAID BASE PORTION HAVING A SLOT IN COMMUNICATION WITH THE BORE OF SAID TUBULAR ARM PROVIDING A PASSAGE FOR ELECTRICAL CONNECTION BETWEEN AN ANTENNA ELEMENT AND A TRANSMISSION-LINE CONDUCTOR, THE ANGULARLYDISPOSED TUBULAR ARMS OF THE Y-FITTINGS AT OPPOSITE ENDS OF SAID INSULATING ROD PROJECTING IN OPPOSING DIRECTIONS. 